Interface Engineering of MXenes for Flexible Energy Storage and Harvesting
Flexible energy storage and harvesting devices, as core components of flexible electronic systems, have driven the transformation from external power supply to self-powering and from fixed forms to adaptive configurations, playing a pivotal role in wearable technology and the Internet of Things. MXenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, are promising candidates due to their excellent conductivity, mechanical flexibility, and tunable interfacial characteristics. Specifically, interfacial characteristics—surface energy, surface terminations, and interlayer spacing—decisively influence device performance. This review summarizes the influence of microcosmic interfacial characteristics on macroscopic properties, interfacial regulation strategies, and applications in flexible energy storage and harvesting. It concludes with challenges and perspectives for designing high-performance MXene-based energy devices. Key applications include flexible supercapacitors, batteries, and triboelectric nanogenerators. For instance, pillared Ti3C2 via CTAB pre-pillaring and Sn4+ pillaring regulates interlayer spacing, enhancing ion transport. The review integrates recent advances, such as MXene/nylon scaffolds for dendrite-free zinc anodes and MXene-bonded hard carbon films for sodium/potassium storage, demonstrating improved cycling stability and rate capability. The interfacial engineering strategies discussed provide a roadmap for overcoming stacking issues and achieving high energy density and mechanical robustness.